1. Field of the Invention
This invention relates to container modules for shipping by rail, truck and ship, and for temporarily storing, dry flowable product which is discharged from the container module under pressure or by gravity.
2. Background Information
Container modules for intermodal shipping are widely used and recently there has been a desire to develop intermodal containers for transport and temporary storage of dry flowable product. Such containers include an elongated tank extending horizontally in a support frame. Examples are shown in U.S. Pat. Nos. 5,390,827 and 5,353,967, incorporated herein by reference. The pressure tank has hatches along the top and loading tubes on the ends for loading and hoppers along the bottom for discharge of the dry, flowable product. While the tank is not normally pressurized during transit, it is typically pressurized to a positive atmosphere (about 14.7 psig) during discharge of its contents and that typically translates to a design pressure (1.5 factor) of about 22 psig. Several dimensional and other criteria for the container modules are set out in International Standard Organization (ISO) standard 1496-4, Series One Freight Container Specification and Testing, Part 4 Nonpressurized Containers, a standard that is well known in the art. The support frame defines an elongated rectangular, parallelpiped envelope for the container module having dimensions which have been standardized for interchangeability. Generally, the envelope is 8 feet wide, 8 feet to 9 and xc2xd feet high, suitably 9 feet 6 inches, and either 20 or 40 feet long. Other standardized features include nodes at each of the eight corners for stacking and lifting the modules. Additional lifting points are also specified. Maximum weights for the loaded modules have been established along with minimum volume requirements, and the tank must be able to withstand specified pressures. The slope of the hopper walls also needs to accommodate desired discharge rates. In addition, room must be provided within the envelope for the plumbing for effecting the pressure discharge of product. The container modules must also satisfy certain rigorous tests which include lifting, static loading, and pressure tests. In addition to the requirements of ISO Standard 1496-4 referred to above, there is the pressurization requirement also mentioned above plus a desired internal tank volume of 1450 or 1500 or more cubic feet, preferably 1550 or 1575 cubic feet or more. Still further, it is desired that the weight of the empty intermodular container (frame, tank and typically limited pneumatic pipes and cones that travel with the container) not exceed 10,000 pounds, or 9500 pounds, preferably 9000 or 8500 pounds. This represents a very substantial weight savings over a stainless steel and steel construction of around 15,000 pounds. Of course, cost is a concern and it is desired to produce a container at reasonable cost.
All of these competing criteria must be reconciled. For instance, maximum volume could be realized by a generally rectangular tank which filled the solid rectangular envelope. However, this would require use of high strength or heavy materials in fabricating the tank to withstand the discharge pressure, thereby adding cost and/or weight. On the other hand, a cylindrical tank could best withstand the pressure using lighter, perhaps less costly materials than the rectangular tank, but with a sacrifice in volume. As an example, a module with a generally rectangular tank is available, but it utilizes stainless steel which adds weight and is expensive. Attempts to duplicate this structure in aluminum have pointed to a serious need for improvement.
There is a need therefore for an improved container module for intermodal transportation and temporary storage of dry flowable product.
There is a more particular need for such a container module which meets volume requirements while minimizing the empty weight of the module.
There is also a need for such a container module which can meet the prescribed pressure specifications without requiring thick, heavy or exotic materials.
There is a further need for such a container module which is strong and durable, and resistant to corrosion by sea air.
There is an additional need for such a container module which has uncluttered space for the necessary discharge plumbing and can be used with a gooseneck truck.
There is yet another need for such a module which meets all of the established specifications and can pass all of the required tests.
There is an overriding need for such a container module which satisfies all the above needs and can be produced economically.
These needs and others are satisfied by the invention which is directed to a container module for intermodal transportation and storage of dry flowable product which includes an elongated support frame having a horizontally extending bottom frame and an upright end frame at each end of the bottom frame, all defining a container envelope of preset dimensions. A tank extends longitudinally along the support frame within the container envelope and has a plurality of downwardly discharging hoppers. Hanger means depending substantially vertically from the end frames engage ends of the tank above the hoppers for suspending the tank from the end frames. The tank has outwardly convex, preferably substantially spherical, end caps which are engaged by the hanger means for suspending the tank. Also, preferably, the hanger means comprises plate members secured to top cross beams and corner posts of the end frames to not only suspend the tank but also to stiffen the end frames.
As another aspect of the invention, the support frame includes corner gussets fixed to the corner posts and the top cross beams and connected to the pressure tank by channel members extending longitudinally along the pressure tank.
As an additional aspect of the invention, the support frame includes elongate members extending longitudinally along each side between the end frame corner posts and secured to each of the hoppers. These longitudinal members resist angular separation of the hoppers through bending of the tank when loaded with dry flowable product or pressurized. They also contribute to the overall structural strength of the container.
In addition, the hoppers along the bottom of the tank are longitudinally intersecting, meaning that the hoppers are spaced longitudinally closer together than their full longitudinal dimension. This increases the volume of the tank white still providing the required slope of the hopper walls for complete discharge of product. The longitudinally intersecting hoppers form girth seams which are spanned by girth plates welded to the adjoining hoppers.
The hopper at the front end of the container module is raised so that its discharge opening is above the discharge openings of the remaining hoppers. This permits the container module to be used with gooseneck trucks. The support frame is also modified at this end by a longitudinal opening which accommodates the gooseneck.
The tank is configured to provide adequate volume for the dry flowable product while withstanding the applied discharge pressure without requiring a thick wall, exotic materials or heavy bracing. To achieve this, the tank has an elongated body portion formed by a wall having a flat upper center section extending no more than about 12 inches laterally, upper curved sections extending laterally and downwardly from the upper center section, flat side sections extending downwardly from the upper curved sections no more than about 12 inches, and curved lower sections which laterally truncate the intersecting downwardly discharging hoppers extending along the bottom of the tank. Preferably, the upper curved sections and lower curved sections are cylindrical sections having radii of about 37 to 45 inches, suitably 40 to 43 or 44 inches. In the 40 foot long embodiment of the invention, there are four to six hoppers and preferably five.
In the preferred embodiment of the invention these hoppers are frusto-conical, although other configurations providing the desired slope of 37 or 40 to 45 or 50 degrees (typically 41 to 45 degrees) and a discharge opening of about 30 inches can be utilized.
All of the above features can be combined to provide a container module which is preferably made all of aluminum except for standardized nodes on each of the corners of the module which are preferably made of steel. Preferably, the tank including the hoppers is made of aluminum plate of no greater than xe2x85x9c inch in thickness and preferably {fraction (5/16)} or xc2xc inch in thickness. Circumferential stiffeners can be provided on the tank body in the form of longitudinally spaced aluminum channels welded across the top flat section and extending around the upper curved sections.
The above features produce a light weight durable, corrosion resistant container module for dry flowable product which can withstand the pneumatic pressures required for product discharge with adequate margin for over-pressure, without the use of exotic materials and at a reasonable cost.